The norm is to wait a week so they can settle, but I just got three new additions this past Tuesday (A Hog BCI, Black Blood, and Angolan) and I fed all of them the day after I got them since they were due a feeding via the breeder's feeding schedule. They all ate without problems, so I'd say it wouldn't hurt to offer before the week's time but the week is the norm for most people, just know that offering without the snake taking it (ie a refusal) could add more stress to it while it's acclimating.